package Persistence;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import Util.ErrorHelper;
import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Helper class for creating, copying, and updating the database.
 * */
public class DatabaseHelper extends SQLiteOpenHelper{
 
    //The Android's default system path of your application database.
    private String _DB_PATH = "/data/data/com.vargas.studypartner/databases/";
    public static String DB_NAME = "sp_.db";
    private final Context _CONTEXT;
    public SQLiteDatabase db; 
     
    /**
     * Constructor
     * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
     * @param context
     */
    public DatabaseHelper(Context context) {
     	super(context, DB_NAME, null, 1);
        this._CONTEXT = context;
    }
 
    /**
     * Creates an empty database on the system and rewrites it with own database.
     * */
    public void createDataBase() throws IOException{
     	boolean dbExist = checkDataBase();
 
    	if(dbExist){
    		return; //do nothing - database already exist
    	}else{
        	this.getReadableDatabase();
        	try {
    			copyDataBase();
     		} catch (IOException e) {
         		ErrorHelper.reportError(this.getClass(), _CONTEXT, e);
         	}
    	}
     }
 
    /**
     * Check if the database already exist to avoid re-copying the file each time you open the application.
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase(){
     	SQLiteDatabase checkDB = null;
 
    	try{
    		String myPath = _DB_PATH + DB_NAME;
    		checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
     	}catch(SQLiteException e){
     		ErrorHelper.reportError(this.getClass(), _CONTEXT, e);
    	}
 
    	if(checkDB != null){
    		checkDB.close();
     	}
 
    	return checkDB != null ? true : false;
    }
 
    /**
     * Copies database from local assets-folder to the just created empty database in the
     * system folder, from where it can be accessed and handled.
     * This is done by transferring bytestream.
     * */
    private void copyDataBase() throws IOException{
     	//Open local db as the input stream
    	InputStream myInput = _CONTEXT.getAssets().open(DB_NAME);
 
    	// Path to the just created empty db
    	String outFileName = _DB_PATH + DB_NAME;
 
    	//Open the empty db as the output stream
    	OutputStream myOutput = new FileOutputStream(outFileName);
 
    	//transfer bytes from the inputfile to the outputfile
    	byte[] buffer = new byte[1024];
    	int length;
    	while ((length = myInput.read(buffer))>0){
    		myOutput.write(buffer, 0, length);
    	}
 
    	//Close the streams
    	myOutput.flush();
    	myOutput.close();
    	myInput.close();
     }
 
    /**
     * Opens the database connection and sets the db instance
     * */
    public void openDataBase() throws SQLException{
     	//Open the database
        String myPath = _DB_PATH + DB_NAME;
    	db = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
     }
 
    /**
     * If the db instance is set, closes the database connection.
     * */
    @Override
	public synchronized void close() {
     	    if(db != null)
    		    db.close();
     	    super.close();
 	}
 
	@Override
	public void onCreate(SQLiteDatabase db) {
 
	}
 
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
 
	}
 
        // Add your public helper methods to access and get content from the database.
       // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
       // to you to create adapters for your views.
 
}
